I think you can't start a business with 20$ but you can do the following to grow these 20$ .
1) you can buy crypto in Payeer and work on the short term profits, for example you can buy Bitcoin, Ethereum, Dash.
You can divide the 20 $ on more than one cryptos the cryptos I mentioned is the best for short term profits.
You can buy on low prices and sell on higer prices.
You can watch and set your price to buy automatically after you buy you can set your sell price to sell automatically too.
2) you can also work online making money through many legit websites, for example completing tasks, answering surveys,clicking ads and more.
You can accumulate these money and use them to start a business or buy sypplies for small business to start with.